Arrangement for equalization and reduction of the pressure upon a stuffing box for apump



June 29, 1965 s m 3,191,540

ARRANGEMENT Eon-E UALIZATION AND REDUCTION OF THE PRESSURE UPON ASTUFFING Box FOR A PUMP Filed Oct. 4, 1963 Fig. I

Fig. 2 #79 5 a7 45 2.9 '7 x 51L v United States Patent 3,191,540ARRANGEMENT FOR EQUALIZATION AND RE- DUCTION OF THE PRESSURE UPON ASTUF- FING 30X FOR A PUMP Arne Skretting, Karlstad, Sweden, assignor toAktiebolaget Kamyr, Karlstad, Sweden, :1 company of Sweden Filed Oct. 4,1963, Ser. No. 313,840 Claims priority, application Sweden, Oct. 6,1962, 10,730/62 1 Claim. (Cl. 103-126) The invention relates to anarrangement for equalization and reduction of the pressure upon astuffing box for the shaft of a rotor of a pump, particularly a pumpadapted for the pumping of stuff of a high viscosity or consistency,such as fibrous suspensions, and in which the rotor is subjected todifferent pressures on opposite sides of its shaft.

In known pumps of said kind the stuffing box for the rotor shaftprojecting through the pump casing is influenced by a pressure which isunevenly distributed over the circumference thereof, a condition whichhas proved to give rise to rapid Wear and leakage. The object of theinvention is to eliminate said drawback and to equalize the pressureupon the stuffing box over its circumference and simultaneously toreduce said pressure to the lowest pressure present in the pump.According to the invention said object is attained essentially therebythat in the wall of the pump casing there is a groove extending allaround the shaft, which groove on the high-pressure side of the pump iscovered by the plane end face of the rotor moving closely adjacent tosaid wall and which groove on the low-pressure side is widened so as toextend beyond said end face, whereby the pressure prevailing on saidlast-mentioned side gets free access to the groove and can spreadthereinto. In order to prevent clogging of said groove a projection maybe provided on the rotor or its shaft, which projection with a suitableclearance fits to the narrowest cross-section of the groove.

An embodiment of the arrangement according to the invention will be moreclosely described herein below with reference to the accompanyingdrawing, in which FIG. 1 is a vertical cross-sectional view of a pumpequipped with the arrangement according to the invention, FIG. 2 is ahorizontal cross-sectional view of one end of the pump, and FIG. 3 is apart of FIG. 2 shown on an enlarged scale.

The pump shown in the drawing is of the cog wheel type and comprises tworotors 11 and 13 which are arranged parallelly and adjacent to eachother and are inserted into a pump casing between the inletside 17thereof where a low pressure prevails, and its outlet side 19 where ahigher pressure prevails in operation due to the action of the pump. Therotors are shaped with projectthe cylindrical wall of the housing,whereas the same number of batches, but each of a considerably smallercontent, are carried back through compartments successively formedbetween the rotors.

The casing 15 has interior plane side walls 27, and the rotors havecorresponding plane end faces 29 moving along said walls as closely aspossible thereto. At either end the rotors are provided with a shaftstud 31 extending through a corresponding aperture in the wall and beingjournalled, eg by means of a ball bearing 33, in a bearing bracket orsimilar attached to the pump casing. Keyed to one end of either rotor isa gear wheel 35 for driving the rotors. The part of the shaft stud 31which is located closest to the rotor end and which preferably iscylindrical, is sealed to an annular flange 37 upon the wall of the pumpcasing by means of a stuffing box which may be composed of a pluralityof rings 39 of a suitable stuffing material put upon the shaft stud 31and let into a bore in said annular flange and clamped thereto. Insertedbetween two of said stuffing rings is an apertured ring 41 whichcommunicates with a bore 43 in the flange 37, said bore forming anoutlet for liquid which may have leaked past the stufiing rings 39 onthe inner side of said apertured ring.

According to the invention, a groove 47 is provided in the Wall 27 inthe immediate vicinity of the bore therein for the shaft stud. On thehigh-pressure side of the pump said groove which preferably is of arectangular crosssection, is so narrow measured in the radial directionof the rotor that it is covered by the end face 29 of the rotor.

I The clearance 49 between the faces 27 and 29 is too slight ing cams orknives 21 each cooperating with a pertaining flute-like depression 23 inthe face of the opposite rotor in such a manner that a seal ismaintained between the rotors during their rotation. The cams 21 alsocooperate with cylindrically curved walls of the pump casing in such amanner that a seal is maintained between the highpressure side and thelow-pressure side of the pump on the far sides of the rotors. When therotors are driven ,in the direction of the arrow 25, successive batchesof the stuff to be pumped, e.g. high-consistency cellulosic pulp, aretransferred from the inlet side to the outlet side of the pump by beingenclosed within and carried forth in compartments successively formedbetween the rotors and to allow passage of fibre material from thehigh-pressure side into said groove 47. Conversely, on the low-pressureside of the pump the groove is widened to such an extent that greatparts thereof are not covered by the end face 29 of the rotor, thepressure prevailing on the low-pressure side of the pump having accessto the groove. Said pressure propagates into the narrow part of thegroove on the high-pressure side of the pump, so that the pressureeverywhere in the groove is the same and equal to the lowest pressurepresent in the pump. In this manner, the pressure upon the stuffing box39 is considerably reduced and besides, said pressure is equal allaround the circumference. Preferably, the measure of the groove in theaxial direction of the rotor is uniform.

Arranged in the angle between the shaft stud 31 and the plane end face29 is a die, boss or similar projection 51 which is shaped to fit intothe narrowest part of the groove 47 with a suitable clearance. The diemay be integral with the rotor or may be manufactured separately andattached, e.g. welded, to the rotor or its shaft stud. During eachrevolution of the rotor said die moves through the narrow part of thegroove and removes fibres which may have escaped thereinto. In thismanner the groove will always be held open all around and the pressureequalization maintained.

I claim:

Means for the equalization and reduction of the pressure upon a stuffingbox for the shaft of a rotor of a pump, particularly a pump adapted forpumping of fibrous sus pensions, and in which the rotor is subjected todifferent pressures on opposite sides of its shaft, comprising a groovein the Wall of the pump casing and encircling said shaft, the groove onthe high-pressure side of said rotor being A. a) covered by the planeend face of the rotor movable close References Cited by the Examiner to'saiti wall and the groove on the low-pressure side be- UNITED STATESPATENTS mg wldened to extend beyond said end face, so that the pressureprevailing on the low-pressure side has free access 1,252,160 1/18 Pagel103L426 to the groove and can spread therein, said rotor being 51,271,968 7/ 18 Wood 103 126 provided with "a projection which fits witha suitable clearance to the narrowest cross-section of the groove andKARL ALBRECHT P'lmary Exammer' serves to prevent clogging of the same.WILBUR J. GOODLIN, Examiner.

